The present disclosure relates to toner conveying devices for conveying toner. More particularly, the present disclosure relates to toner conveying devices provided with a toner conveying portion in which a horizontal conveying portion is connected to a bottom end part of a vertical conveying portion for making toner fall vertically, and to developing devices and image forming apparatuses provided with such a toner conveying device.
Image forming apparatuses such as electrophotographic printers and copiers include a photosensitive drum which carries an electrostatic latent image, a developing device which feeds toner to the photosensitive drum to develop the electrostatic latent image into a toner image, and a toner container which feeds toner to the developing device. In some color image forming apparatuses, a layout in which an intermediate transfer unit is provided between the toner container and the developing device is adopted. In this case, since the toner container is away from the developing device, a toner conveying portion for conveying toner from a toner discharge port of the toner container to a toner receiving port of the developing device is provided.
Here, when the toner container can be arranged right above the developing device, only a vertical conveying portion for making toner fall vertically has to be provided in the toner conveying portion. However, when it is difficult to arrange the toner container right above the developing device due to limitations in layout, a horizontal conveying portion for conveying toner horizontally is required in the toner conveying portion in addition to the vertical conveying portion. In the horizontal conveying portion, a conveying screw for conveying toner is arranged.
In the toner conveying portion in which the horizontal conveying portion is connected to the vertical conveying portion, inconveniently, toner can agglomerate around the bottom end part (the connecting part with the conveying passage) of the vertical conveying portion to hamper smooth toner feeding. This is caused by toner agglomerates blocking the conveying passage resulting from the toner around the bottom end of the vertical conveying portion being pushed back upward by the rotation of the conveying screw.
To solve the problem mentioned above, there is a known technique of fitting a twisted coil spring that vibrates with the rotation of the conveying screw to the conveying screw. With this configuration, it is possible to prevent toner from agglomerating in the vibrating range of the twisted coil spring.
With the above method, it is not possible to loosen toner agglomerates generated above the vibration range of the twisted coil spring. Since it is difficult to make a long twist coil spring for such use, a method for reliably loosening toner in the vertical conveying portion has been sought.
Thus, there is a known configuration where a swingable ball which can make contact with both the toner loosening member and the conveying screw is arranged near the connecting part between the vertical and horizontal conveying portions. With this configuration, the contact portion of the swingable ball changes between the screw shaft of the conveying screw and the blade portion of the conveying screw as the conveying screw rotates and this makes the toner loosening member swing vertically.